Carbon nanotubes—a material discovered in the early 1990s—have many desirable properties. For example, carbon nanotubes can have desirable mechanical properties such as high stiffness, toughness, and resilience. As another example, carbon nanotubes can have desirable electrical properties such as electrical conductivity. Because of these and/or other properties, carbon nanotubes may be a promising material from which to construct probes for use in such applications as atomic force microscopes (see United States patent application US 2007/0051887). However, such probes are inherently weak in a vertical direction and can be easily deformed past the point of effective use when the probe comes into pressure contact with a surface which causes buckling or deformation the carbon nanotube.
Resilient, compliant, deformable, or elastic probes (whether mechanical or electromechanical) are typically made of materials other than carbon nanotubes have been used in various applications. For example, a group (e.g., an array) of probes can be placed in a pattern that corresponds to a pattern of objects to be probed (e.g., physically contacted) by the probes. Such probes can be electrically conductive and can contact input and/or output terminals of an electronic device (e.g., a semiconductor die or dies) to establish temporary pressure based electrical connections with the electronic device through which test signals can be provided to the electronic device and response signals generated by the electronic device can be sensed. Through such testing, electronic devices can be evaluated to determine whether the devices function properly and/or rate operation of the devices.
Depending on the specific probing application, it can be desirable for such probes to have one or more particular mechanical properties. For example, in some applications, it can be desirable for the probes to be compliant and resilient in response to a force applied to the probes. For example, such a probe can be compliant by compressing, deforming, bending, or otherwise moving in response to a force applied to a contact portion of the probe, and the probe can be resilient by generating a counter force in response to the force applied to the contact portion of the probe and then substantially returning to the original shape, position, or orientation of the probe after the applied force is removed from the contact portion of the probe. It can be desirable in some applications to tune the probes to have particular mechanical properties. Other mechanical properties such as toughness, durability, and consistency through repeated use over an extended period of time can also be desirable. For example, it can be desirable for such probes to withstand repeated compressions over extended periods of time without undergoing substantial changes in mechanical properties.
In addition, if the probing application is electrical, it can be desirable for such probes to have one or more particular electrical properties. For example, in some applications, it may be desirable that electrical probes have a low electrical resistance and/or a high current carrying capacity.
Regardless of whether the probing application is electrical, it can be desirable for the probes to have other desirable properties such as manufacturability. For example, in some applications, there may be a need to form the probes in a pattern (e.g., an array) in which the probes are spaced close to one another (e.g., the pitch or spacing between probes is small). In such applications, it may be desirable for the probes, although spaced close to one another, to be able to compress, deform, bend, or otherwise move in response to forces (e.g., exhibit compliance) applied to the probes without the probes contacting or otherwise interfering with each other. In some applications, it can be desirable to planarize contact portions (e.g., contact tips) of the probes so that the contact portions of all of the probes in the group are located within a specified distance of a special plane. In some applications, it can be desirable for the probes to be able to withstand repeated use at extreme temperatures (e.g., high temperatures or low temperatures). Of course, it can be desirable to be able to efficiently and economically make such probes and/or incorporate such probes into a probing apparatus.
Some embodiments of the invention described below can, in some instances, aid in the production and/or use of probes comprising carbon nanotubes that have one or more of the foregoing desirable mechanical, electrical, manufacturability, or other properties.